Bluetooth is one of the short-range wireless communications technologies making it possible for real-time data communication between electronic devices. Since the development of Bluetooth, many versions of Bluetooth standards have been released, and the standardization of low-power communication solutions has increased the application fields of Bluetooth. As with other communication technologies, in Bluetooth communication a data rate, low power consumption, and coverage extension are important factors.
In comparison with the legacy Bluetooth (BT), Bluetooth low energy (BLE) as an extension of Bluetooth focused on low power is attracting growing interest in terms of its low-power, low-cost, simplicity, and compact design.
Bluetooth devices have respective communication coverage ranges determined according to their specifications and may communicate among each other in overlapping coverage. For example, Bluetooth devices may be manufactured with different Bluetooth chips to meet device-specific hardware requirements. Because of the difference in Bluetooth chip and mechanical characteristics (e.g., antenna and metal housing), the data communication specifications (e.g., coverage range) of the Bluetooth devices may be different. For example, a communication standard (e.g. 1M physical layer (Phy)) may have a coverage range that is greater than that of a second communication standard (e.g., 2M Phy) and a data rate that is less than that of the second communication standard.
It may be that a physical layer protocol changes between two Bluetooth devices in communication, resulting in Bluetooth channel breakdown and data communication failure.
If a predetermined condition is fulfilled in the course of communication between two Bluetooth devices at the symbol rate of 1M sym/s, it may be possible to change the physical layer protocol to increase the symbol rate to 2M sym/s. In this case, if one of the two Bluetooth devices is out of the coverage range of the other for data communication at the symbol rate of 2M sym/s, the communication channel is broken down. For example, it may be possible for a device entered in the 1M sym/s communication coverage range of another device to receive a first information through a 1M sym/s communication channel and then want to receive a second information (e.g., advertisement information) through the 2M sym/s communication channel. However, if the device is out of the 2M sym/s communication coverage range of another device, it cannot receive the second information.